Police said a 15kg bomb had been planted in a vehicle parked outside the minister's home.

Further north, a roadside bomb killed at least 10 people and wounded four in Pakistan's Kurram tribal region on the Afghan border.

The explosion occured in Palaseen village, about 65km northeast of the region's main town, Parachinar, a government official said.

Hamid Khan, a deputy administrator of the region, said: "It was a remote-controlled bomb, which was detonated as soon as a passenger van got there. Those killed were all civilians."

Fighters linked to al-Qaeda have recently stepped up bomb and suicide attacks in Pakistan after a brief lull amid the worst flooding in the country's history.

More than 150 people have been killed in the renewed violence in the last week.

Drone strikes

The Pakistani Taliban has threatened to carry out more suicide attacks on government targets in response to US drone raids in Pakistan's tribal regions in the northwest.

Earlier on Thursday, a suspected US missile attack - the fourth raid in 24 hours - hit North Waziristan, the same tribal district targeted in three other drone attacks since Wednesday and a known hub of Taliban and al-Qaeda-linked fighters.

The target of the fourth attack was a compound in the outskirts of Miranshah, the main town in North Waziristan.

In the last 24 hours, four drone attacks have killed at least 24 suspected Taliban fighters. There was no independent confirmation of the deaths, and the Taliban often disputes government accounts.

Journalist freed

Against the backdrop of violence, the British high commission confirmed on Thursday that Asad Qureshi, a British journalist held captive in Pakistan since March, has been released.

Qureshi was abducted in the northwest tribal region while filming a report on fighters there with a retired Pakistani army officer and a former intelligence agent.

"We can confirm Asad Qureshi has been released and our consular team are providing him with consular assistance," George Sherriff, a spokesman for the British high commission in Islamabad, said.

A little-known group called Asian Tigers had captured the trio, apparently killing Khalid Khawaja, the former spy, in April because the government refused to co-operate with their demands. His body was found in Mir Ali town in North Waziristan.

The fate of the third hostage, Sultan Ameer Tarar, a retired military officer known as "Colonel Imam", remained unclear.